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Herein, the filling of single‐walled carbon nanotubes (SWCNTs) with sulfur is performed, and the magnetic properties of the formed nanomaterials are studied. Encapsulation of sulfur species results in the appearance of a specific magnetic ordering in the system due to the formation of nanoscopic grains composed of sulfur and residual catalytic Fe nanoparticles contained in the SWCNTs. The magnetic character of the obtained 1D nanostructures is studied using superconducting quantum interference device (SQUID) magnetometer and a sequential ferromagnetic–antiferromagnetic ordering in the material is revealed. Magnetic and optical properties are strongly dependent on the synthesis protocols. A significant Raman intensity increase related to the encapsulated nanostructures is obtained when filling is performed at high‐pressure high‐temperature conditions. Simultaneously, the magnetic susceptibility gets strongly reduced for high‐pressure filling, which is related to the escape of iron particles from the nanotube interior, and the magnetic properties of the material are governed by a weak ferromagnetic ordering of Fe–S structures remained inside SWCNTs. Sulfur encapsulation provides the new route for controlling the magnetic properties in 1D nanomaterials that pave the way for advanced magneto‐optical applications. [ABSTRACT FROM AUTHOR]

Highlights • A small variation in composition leads to fundamental changes in magnetic properties. • Drastic violation of the correlation between the anomalous Hall effect (AHE) and ordinary resistivity. • Resistivity and anomalous Hall effect are determined by different groups of current carriers. • Transformation of the electronic structure as the driving mechanism of martensitic transition. Abstract Two metamagnetic Heusler alloys based on Ni 45 Cr 5 Mn 37 In 13 with differing Mn concentrations (by 0.2 at. %) were studied using magnetization, resistivity, and Hall resistivity measurements. It is shown that this small variation in composition leads to fundamental changes in magnetic properties. Near the martensitic phase transitions, the anomalous Hall coefficient (R S) was found to increase with temperature while the resistivity (ρ) decreases. Thus, in the case of Ni 45 Cr 5 Mn 37 In 13 , the general correlation between R S and ρ, considered as applicable for all crystalline and amorphous ferromagnetic alloys, breaks down completely. We explain this behavior in the framework of an s-d model where it is assumed that the resistivity and anomalous Hall effect are determined by different groups of current carriers. [ABSTRACT FROM AUTHOR]